MCLEAN, Va. — As his tenure comes to a close, Metro General Manager Richard Sarles made one last push for the long-term plan known as Metro Momentum to key lawmakers and other decision-makers.

At a presentation hosted by the Northern Virginia Transportation Alliance, Sarles said it was critical to expand all trains to eight cars in the next 10 years to combat the crunch riders feel each morning.

Creating a full fleet of such trains, plus finding other ways to ease congestion at choke points such as Rosslyn, Virginia, are the biggest components of the 10-year vision.

Part of the move will begin early next year, when the first 7000-series rail cars go into service.

The first 7000-series cars arrived last year, and 64 more will be delivered before July 2015. In total, Metro will have 528 new rail cars — 300 will replace the 1000-series. Another 100 will replace the 4000-series cars. The final 128 will be new cars to expand the fleet.

A key date for Metro comes next August. Metro has an option to purchase another 220 new rail cars from manufacturer Kawasaki.

Sarles says exercising the option will make it more likely for Metro to reach its goal by 2025.

But, he says, not exercising the option would set Metro back five years and make a big dent in the 2025 plan.

So far, D.C., Maryland and Virginia have not committed the full money to pay for the additional cars.

However, Sarles notes that it’s not just the rail cars themselves: Metro needs more money to upgrade its power systems and add new substations. It also needs more money for rail yards to store all these new rail cars when they’re not being used.